Incandescent bulbs that "last forever"...but there's a hitch.

As I worked my way through the solar workshop podcasts, the idea came up that the evil planned obsolescence incandescent light bulb companies ...make their light bulbs wear out prematurely. They went on to mention that you can buy, pretty inexpensively, 130V incandescent light bulbs that last for literally thousands of hours. This is much longer than the wimpy 1000 to 1,500 rated hours of normal bulbs.

So, why don't we all use those?

Why indeed...there's a catch.

If you run the tungsten filament a less than the rated voltage, it will last a lot longer. There are legitimate examples of light bulbs running continuously for -decades- before burning out.

The problem is, you don't get as much light out.

So there's the catch. It lasts longer, but the lumens per watt drops off pretty fast. Less efficient at converting electricity to light.

Various opinions suggest that for a 12-15% reduction in voltage, you get a 25% reduction in lumens. Over the life of the lamp, the money you saved on lamp replacement would be more than made up for in the extra electricity to provide the same lumens.

I.e. you will probably have to put a 75W 130V bulb in to replace a 60W 120V bulb to get the same apparent brightness.


130V bulbs make a lot of sense if you get a lot of voltage spikes and you are burning out 120V bulbs at a furious pace, or if the bulb in in a location that is inconvenient or dangerous to replace.

There's no wrong answer here, provided you understand the trade off you're making.

troy

Or, you can have a thicker filament, and you'll need a lot of energy to generate the light. Which is probably just me saying the same thing in non electrician talk.

That is exactly what a 130 V light bulb is, just a heavier filament.

troy

It's true about that trade-off
Aero-Tech etc make legal "rough service" bulbs for the mining industry etc (that can be used domestically)
20 000 hrs plus, but as you say with that trade off.

However there is a bigger picture
It does not have to occur below about 5000 hours anyway
Yet 1000 hours is the standard (750 hrs for 100W, US)
This relates to the Phoebus Cartel between the major manufacturers that limited lifespan to increase sale and profits
Paul here (Paul Wheaton) amusingly covers this on his video Mr Stinkypants


As it happens recent research in Germany and USA with different books has also covered this
Links via
http://freedomlightbulb.org/p/how-bans-are-wrongly-justified.html#industrypol

The same manufacturers then went on to lobby for the ban on patent expired cheap relatively unprofitable incandescents,
as also covered there and on Paul's video